This invention relates to a diesel engine and more particularly to a precombustion form of diesel engine that is particularly adapted for use in motor vehicles.
In many regards, diesel engines have a number of advantages over spark ignited engines. The utilization of diesel engines has, to a large part, been limited to large type vehicles such as trucks or the like. In a similar manner, in marine vehicles diesel engines are frequently as used a power plants, but again their usage is primarily with larger type watercraft.
There is, therefore, a demand for a relatively small yet high performance diesel engine that can be employed to fill the market for high efficiency, small displacement engines for vehicle application. By utilizing a small two-cycle diesel engine, it is possible to obtain relatively large power outputs for a given displacement. Hence, two-cycle diesel engines of small displacement may have considerable utility in conjunction with vehicles and particularly those of smaller sizes.
One problem that has precluded the wider utilization of diesel engines, particularly in small displacements, is the difficulty in starting and maintaining combustion in the combustion chamber. It has been proposed, therefore, to use a so-called torch or precombustion chamber which is formed generally in the cylinder head and which communicates with the main combustion chamber through a throat opening. The way this type of engine operates is that, as the piston approaches top dead center position and the charge is compressed, the charge which is transferred into the precombustion chamber will be compressed to a high degree. If the fuel for combustion is injected primarily into this pre-combustion chamber, it will be better assured that combustion will initiate because a stoichiometric mixture will clearly be present.
The burning fuel then expands in the precombustion or torch chamber and enters the main chamber along with additional fuel where burning can continue. Hence, this type of arrangement has considerable advantages.
It is important, however, to provide appropriate positioning of the throat area and the precombustion chambers so that the direction of flow of the burning gases and additional fuel into the combustion chamber will well mix in the combustion chamber. Also, when utilized with two-cycle engines, the direction of flow should be such that it will minimize the amount of fresh charge that can pass out of the exhaust port during or even before the time period when the exhaust port is open.
This problem is particularly acute because of the fact that the exhaust port is valved by the piston as it reciprocates in the cylinder bore. It is well known that the piston operation coupled to its connection to the connecting rod causes the piston to rock slightly in the cylinder bore. This rocking motion can open up a clearance area between the head of the piston and the cylinder bore. If the injected charge and the flow from the torch chamber can pass into this gap, it may well escape from the exhaust port and, thus, render inefficient combustion.
It is, therefore, a principal object of this invention to provide an improved diesel engine.
It is a further object of this invention to provide an improved two-cycle, crankcase compression, diesel engine applicable for utilization in a motor vehicle.
It is a still further object of this invention to provide an improved torch or precombustion chamber for diesel engines that facilitates their use with two-cycle crankcase compression engines so as to achieve high power outputs from small displacements.